Sustainable and resourceful utilization of garden waste with high lignocellulosic content remains a huge challenge, anaerobic digestion (AD) and hydrothermal treatment provide prospective technologies with achieving environmental and economic benefits. In this study, a 7–28 d AD was provided as a biomass pretreatment means and combined with hydrothermal carbonization (HTC) to treat three typical garden wastes (leaves, branches, grass). The results showed that AD pretreatment could effectively change the surface composition and structure properties of the feedstocks and thus modulating the properties of the hydrochar downstream. Compared to the unpretreatment samples, the specific surface area (SSA), higher heating value (HHV), energy density and nutrient elements (P and K) of hydrochar obtained by AD pretreatment were significantly improved and enriched, respectively. Specifically, the highest HHV of hydrochar obtained from leaves, branches, and grass were 25.71, 25.63, and 23.81 MJ/kg, which obtained with 21, 14, and 7 d of AD pretreatment respectively. The P contents of hydrochar of leaves and grass pretreated with AD for 14 and 7 d were 205% and 15% higher than those without AD pretreatment, respectively. Additionally, in this coupled system, the biomass energy recovery of 90.2% (78.2% biochar and 12.0% CH₄) was achieved on leaves pretreated with AD for 21 d. Energy recovery of 81.2% (66.8% biochar, 14.4% CH₄) and 71.3% (39.7% biochar, 31.6% CH₄) was obtained by 14 d of AD pretreatment on branches and grass, respectively. Thus, this study enhances energy utilization efficiency and reduces secondary waste generation, providing valuable new insights into AD coupled with HTC technology.

可持续和资源化利用高木质纤维素含量的花园垃圾仍然是一个巨大的挑战，厌氧消化 (AD) 和水热处理提供了实现环境和经济效益的前瞻性技术。在本研究中，提供 7-28 d AD 作为生物质预处理手段，并结合水热碳化 (HTC) 处理三种典型的园林废物（树叶、树枝、草）。结果表明，AD 预处理可以有效地改变原料的表面组成和结构特性，从而调节下游氢化物的特性。与未经预处理的样品相比，比表面积（SSA）、热值（HHV）更高，AD预处理获得的水炭的能量密度和营养元素（P和K）分别显着提高和富集。具体而言，从叶子、树枝和草中获得的水焦的最高 HHV 分别为 25.71、25.63 和 23.81 MJ/kg，分别在 AD 预处理 21、14 和 7 d 下获得。AD预处理14天和7 d的叶片和草的水碳P含量分别比没有AD预处理的高205%和15%。此外，在这个耦合系统中，生物质能源回收率为 90.2%（78.2% biochar 和 12.0% CH AD预处理14天和7 d的叶片和草的水碳P含量分别比没有AD预处理的高205%和15%。此外，在这个耦合系统中，生物质能源回收率为 90.2%（78.2% biochar 和 12.0% CH AD预处理14天和7 d的叶片和草的水碳P含量分别比没有AD预处理的高205%和15%。此外，在这个耦合系统中，生物质能源回收率为 90.2%（78.2% biochar 和 12.0% CH₄ ) 在用 AD 预处理 21 天的叶子上实现。通过对树枝和草进行 14 天的 AD 预处理，分别获得了81.2%（66.8% 生物炭，14.4% CH ₄）和 71.3%（39.7% 生物炭，31.6% CH ₄）的能量回收率。因此，这项研究提高了能源利用效率并减少了二次废物的产生，为 AD 与 HTC 技术相结合提供了宝贵的新见解。